1. Field of the Invention
This invention is related to a light emitting diode (LED) device; more specifically it is related to a white LED package structure and its packaging methods.
2. Background Art
As a semiconductor lighting device, LED has superior advantages over traditional lighting devices, such as incandescent bulb and fluorescent tube, with a longer life time, a more compact size, a lower applied voltage source, no mercury pollution, and a more energy saving property. Therefore it is called the first option of the green lighting sources, and has already been widely used in signal light, display, and LCD backlighting. There is also a trend for the LED to replace the incandescent and fluorescent in general illumination area.
In a traditional method for making a white LED, the phosphor containing layer is directly dispensed onto and cover the surfaces of a blue or UV LED die so that the excited light from the phosphor with various wavelengths mixed together or mixed together with the excitation light if the excitation light is blue to create a white light emission. In this method, the LED suffers a great light absorption loss when the emitted light from the phosphor propagates backwardly into the LED die or to the substrate area around the LED die because of close proximity between phosphor and the LED die. An improving method is to separate the phosphor containing layer from the LED die by using a transparent spacer, such as a silicone, to reduce the chance of the excited emission from the phosphor to hit back into the LED die or the substrate area around the die. This has been described in the U.S. Pat. No. 5,959,316 as the prior art shown in FIG. 3. In FIG. 3, an LED die (60) is attached onto a substrate (62, and the phosphor containing layer (66) is separated from the LED die (60) by using a transparent spacer (64); outside the phosphor containing layer (66) is a protective transparent layer (68). The LED die is electrically connected to the substrate (62) by using gold wires. In this structure, the emitted light from the phosphor layer in a back forwarding direction can still hit the LED die or the substrate area around the die without any obstacle, causing light absorption.